1. Field of the Invention
The present invention relates to a liquid crystal display.
2. Discussion of the Background
A liquid crystal display (LCD) is one type of widely used flat panel displays (FPDs). The LCD is composed of two display panels on which field generating electrodes such as pixel electrodes and a common electrode are formed, and a liquid crystal layer is disposed between the two display panels. A voltage is applied to the field generating electrodes to generate an electric field in the liquid crystal layer, which determines an orientation of liquid crystal molecules of the liquid crystal layer that controls a polarization of incident light passing through the liquid crystal layer to display an image.
A vertical alignment (VA) mode LCD has the liquid crystal (LC) molecules aligned with their long axes perpendicular to the display panels in the absence of the electric field. The VA mode LCD is of interest because of its high contrast ratio and wide reference viewing angle.
In the VA mode LCD a plurality of domains in which the alignment direction of the liquid crystal molecules within respective domains are different from the alignment direction of the liquid crystal molecules in the other domains may be formed in one pixel to achieve the wide reference viewing angle.
Methods in which a minute slit or a cutout is formed in the field generating electrodes or a protrusion have been proposed as means for forming the plurality of domains in one pixel. In this method, the plurality of domains may be formed by aligning the liquid crystal molecules vertically with respect to a fringe field generated between the edges of the cutout or the protrusion and the field generating electrodes facing the edges.
Also, a light alignment method in which light is irradiated to an alignment layer to control an alignment angle and alignment direction of the liquid crystal molecules has been proposed as another way to form the plurality of domains in one pixel.
On the other hand, the liquid crystal display of the VA mode may have lower side visibility compared with front visibility. Thus, one pixel may be divided into two subpixels, and different voltages may be applied to the subpixels to solve this problem.
Among the various methods for applying a different voltage to each subpixel, one method applies one data voltage to two subpixels, and then a charged voltage of one subpixel is pulled down and a charged voltage of the other subpixel is raised up through a boosting capacitor such that the visibility may be improved by differentiating the voltages of the two subpixels without a reduction of the aperture ratio due to increasing the number of data lines or gate lines. Also, a decrease of luminance due to capacitive coupling of two subpixels may be eliminated.